1. Field of the Invention
The present invention relates generally to mattress construction. More precisely, the present invention relates to a mattress having an anti-roll off feature.
2. Description of the Prior Art and Related Information
In conventional mattresses for use as beds, it is important to have a more firm or rigid perimeter surrounding a less firm body. Due to wear and tear, typically, the edge of a conventional mattress might sag, shift, lose its form, etc. A sleeper lying on the mattress might inadvertently roll off the mattress due to the lack of support at the sagging edge. To overcome this problem, there have been many approaches to designing a mattress with an anti-roll off feature.
Most improvements focus on the innerspring unit of the mattress. The innerspring unit is usually made from a plurality of spring coils arranged side-by-side in a rectangular matrix. A border made of metal wires encircling both the upper and lower surfaces frame the innerspring. The plurality of helical spring coils are positioned in a spaced apart relationship within the innerspring unit to provide the internal support for the mattress.
Some examples of anti-roll off mattresses using a modified innerspring unit are disclosed in the following. U.S. Pat. No. 4,286,344 to Ikeda discloses an anti-roll off mattress that includes a pair of ridges formed on a sheet of elastomeric material that covers both sides of an innerspring unit. The elastomeric material is attached to the innersprings. U.S. Pat. No. 5,239,715 to Wagner discloses a border stabilizing and reinforcing member for use in mattresses. Specifically, a plurality of rhomboid-shaped members of resilient material are placed in the innerspring unit of a mattress between adjacent rows of springs. When placed as a beam between the springs, the rhomboid-shaped members improve firmness of the mattress.
U.S. Pat. No. 5,537,699 to Bonaddio et al. discloses a mattress border construction including a foam rail sleeve encasing a single row of coiled springs so that the top, bottom, and sides of the row of springs are surrounded by foam. Essentially, the coiled springs encased in the foam sleeve reinforce the border or edges of the innerspring unit giving it strength.
Another method of preventing roll-off is a mattress topper pad consisting of sheets of foam padding wherein the soft foam is located in the middle of the sheet and the hard foam is located at the periphery or edges. Two or three of these sheets are laid on top of the innerspring unit in order to achieve the anti-roll off effect.
Other conventional methods of creating an anti-roll off mattress include a bed guard comprising at least one elongated bolster assembled on top of a conventional mattress held in a position along one edge of the bed. A plurality of bolsters may be used on each edge of the bed for additional roll-off protection. Another design suggests using an array of pockets in which cylindrically shaped foam members are inserted to define a retainer structure enclosing a sleeping area on the mattress. Another conventional mattress design suggests using elastic foamed block inserts positioned into the void spaces left in the innerspring assembly at the periphery of the mattress. Still another prior art design mattress teaches a mattress topper pad and border stabilizer means for mattress innerspring units. The topper pad portion overlies the top or bottom of the coil innerspring unit while the border stabilizer portion is inserted between at least one convolution of each coil on the outside row of the coil innerspring unit to stiffen the spring action of the coils.
Another conventional mattress is constructed with a sleep surface or an overlying sheet on the mattress to produce a raised portion thereof. In another mattress design, the mattress has an upper surface that tapers from the head end toward the foot end. The mattress has an upwardly extending rolled rim on both sides of the mattress to increase the comfort for the sleeper and to prevent the sleeper from accidentally rolling off the bed. Examples of the foregoing mattress construction technology are discussed in, for example, U.S. Pat. No. 4,872,228 to Bishop; U.S. Pat. No. 4,607,402 to Pollard; U.S. Pat. No. 3,848,283 to Ikeda; U.S. Pat. No. 3,822,426 to Mistarz; U.S. Pat. No. 3,148,387 to Sarnie; and U.S. Pat. No. 1,432,875 to Lavagetto. There is, however, still a need for an improved anti-roll off mattress that is durable, and is economical and easy to manufacture.